<?php

/*
 * This file is part of the PHPASN1 library.
 *
 * Copyright © Friedrich Große <friedrich.grosse@gmail.com>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */
namespace RSSProVendor\FG\ASN1\Universal;

use Exception;
use RSSProVendor\FG\ASN1\Exception\ParserException;
use RSSProVendor\FG\ASN1\Parsable;
use RSSProVendor\FG\ASN1\Identifier;
class BitString extends OctetString implements Parsable
{
    private $nrOfUnusedBits;
    /**
     * Creates a new ASN.1 BitString object.
     *
     * @param string|int $value Either the hexadecimal value as a string (spaces are allowed - leading 0x is optional) or a numeric value
     * @param int $nrOfUnusedBits the number of unused bits in the last octet [optional].
     *
     * @throws Exception if the second parameter is no positive numeric value
     */
    public function __construct($value, $nrOfUnusedBits = 0)
    {
        parent::__construct($value);
        if (!is_numeric($nrOfUnusedBits) || $nrOfUnusedBits < 0) {
            throw new Exception('BitString: second parameter needs to be a positive number (or zero)!');
        }
        $this->nrOfUnusedBits = $nrOfUnusedBits;
    }
    public function getType()
    {
        return Identifier::BITSTRING;
    }
    protected function calculateContentLength()
    {
        // add one to the length for the first octet which encodes the number of unused bits in the last octet
        return parent::calculateContentLength() + 1;
    }
    protected function getEncodedValue()
    {
        // the first octet determines the number of unused bits
        $nrOfUnusedBitsOctet = chr($this->nrOfUnusedBits);
        $actualContent = parent::getEncodedValue();
        return $nrOfUnusedBitsOctet . $actualContent;
    }
    public function getNumberOfUnusedBits()
    {
        return $this->nrOfUnusedBits;
    }
    public static function fromBinary(&$binaryData, &$offsetIndex = 0)
    {
        self::parseIdentifier($binaryData[$offsetIndex], Identifier::BITSTRING, $offsetIndex++);
        $contentLength = self::parseContentLength($binaryData, $offsetIndex, 2);
        $nrOfUnusedBits = ord($binaryData[$offsetIndex]);
        $value = substr($binaryData, $offsetIndex + 1, $contentLength - 1);
        if ($nrOfUnusedBits > 7 || $contentLength - 1 == 1 && $nrOfUnusedBits > 0 || (ord($value[strlen($value) - 1]) & (1 << $nrOfUnusedBits) - 1) != 0) {
            throw new ParserException("Can not parse bit string with invalid padding", $offsetIndex);
        }
        $offsetIndex += $contentLength;
        $parsedObject = new self(bin2hex($value), $nrOfUnusedBits);
        $parsedObject->setContentLength($contentLength);
        return $parsedObject;
    }
}
